BS EN ISO 11212-3-1997 Starch and derived products Heavy metals content Determination of lead content by atomic absorption spectrometry with electrothermal atomization《淀粉和淀粉制品 重金属含.pdf

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1、BRITISH STANDARD BS EN ISO 11212-3:1997 Starch and derived products Heavy metals content Part 3: Determination of lead content by atomic absorption spectrometry with electrothermal atomization This European Standard EN ISO 11212-3:1997 has the status of a British Standard ICS 67.180.20BS EN ISO 1121

2、2-3:1997 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Board, was published under theauthority of the Standards Board and comes into effect on 15 May 1997 BSI 01-1999 ISBN 0 580 27456 X National foreword This British Standard is the Engl

3、ish language version of ENISO 11212-3:1997. It is identical with ISO 11212-3:1997 and implements it as the UK national standard. This British Standard has been produced to fulfil BSIs obligation to implement all European Standards but, because of the absence of interest in the UK in the subject conc

4、erned, there has been no UK participation in the preparation of ENISO 11212-3. Any queries relating to the EN should be directed to BSI, quoting the reference AW/100. Cross-references The British Standards which implement international or European publications referred to in this document may be fou

5、nd in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards a

6、re responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN ISO title page, page 2, the ISO title page, page ii, pages

7、 1 to 4 and aback cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBSEN ISO 11212-3:1997 BSI 01-1999 i Contents Page

8、National foreword Inside front cover Foreword 2 Text of EN ISO 11212-3:1997 1ii blankEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 11212-3 March 1997 ICS 67.180 Descriptors: See ISO document English version Starch and derived products Heavy metals content Part 3: Determination of lead con

9、tent by atomic absorption spectrometry with electrothermal atomization (ISO 11212-3:1997) Amidons, fcules et produits drivs Teneur en mtaux lourds Partie 3: Dtermination de la teneur en plomb par spectromtrie dabsorption atomique avec atomisation lectrothermique (ISO11212-3:1997) Strke und Strkederi

10、vate Schwermetallgehalt Teil 3: Bestimmung des Bleigehaltes durch Atomabsorptionsspektrometrie mit elektrothermischer Atomisierung (ISO 11212-3:1997) This European Standard was approved by CEN on 1997-02-28. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate th

11、e conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. The European Standards exist in

12、three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of

13、 Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretaria

14、t: rue de Stassart 36, B-1050 Brussels 1997 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 11212-3:1997 EENISO 11212-3:1997 BSI 01-1999 2 Foreword The text of the International Standard ISO 11212-3:1997 has been prepared by Te

15、chnical Committee ISO/TC 93 “Starch (including derivatives and by-products)” in collaboration with CEN/CS. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September 1997, and conflicting national

16、standards shall be withdrawn at the latest by September 1997. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Irelan

17、d, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of the International Standard ISO11212-3:1997 was approved by CEN as a European Standard without any modification. Contents Page Foreword ii 1 Scope 1 2 Definition 1 3

18、Principle 1 4 Reagents 1 5 Apparatus 1 6 Procedure 2 7 Expression of results 3 8 Precision 3 9 Test report 3 Annex A (informative) Results of interlaboratorytest 4 Figure 1 Digestion apparatus 2 Table A.1 Interlaboratory test on corn starch 4EN ISO11212-3:1997 ii BSI 01-1999 Foreword ISO (the Intern

19、ational Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has b

20、een established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical sta

21、ndardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least75% of the member bodies casting a vote. International Standard ISO11212-3was prepared by Technical Co

22、mmittee ISO/TC93, Starch (including derivatives and by-products). ISO11212consists of the following parts, under the general title Starch and derived products Heavy metals content. Part 1: Determination of arsenic content by atomic absorption spectrometry; Part 2: Determination of mercury content by

23、 atomic absorption spectrometry; Part 3: Determination of lead content by atomic absorption spectrometry with electrothermal atomization; Part 4: Determination of cadmium content by atomic absorption spectrometry with electrothermal atomization. Annex A of this part of ISO11212is for information onl

24、y. Descriptors: Starches, food starch, chemical analysis, determination of content, heavy metals, lead, atomic absorption spectrometric method.EN ISO 11212-3:1997 BSI 01-1999 1 1 Scope This part of ISO11212 specifies a method for the determination of the lead content of starch, including derivatives

25、 and by-products, by atomic absorption spectrometry with electrothermal atomization. The number of parameters for the procedure involved in the electrothermal atomization is far larger than in flame atomization; it is thus impossible to propose a comprehensive method likely to ensure the attainment

26、of satisfactory results on all types of apparatus currently available. Each analyst should therefore optimize the conditions of use of his/her own apparatus on the basis of general or particular instructions. 2 Definition For the purposes of this part of ISO11212, the following definition applies. 2

27、.1 lead content quantity of lead determined in accordance with the conditions specified in this method and expressed as lead (Pb), in micrograms per kilogram of the product as received 3 Principle Wet digestion of the organic matrix. Injection of an aliquot portion of digested sample, in the presenc

28、e of a matrix modifier, into the furnace of an electrothermal atomization atomic absorption spectrometer. Measurement of the absorbance at a wavelength of283,3nm. Determination of the concentration of lead in the sample by means of a calibration curve. 4 Reagents Use only reagents of recognized anal

29、ytical grade and distilled water or water of equivalent purity. 4.1 Nitric acid (r 20=1,38g/ml). 4.2 Hydrogen peroxide, 30% (V/V) solution. 4.3 Matrix modifier, of the following composition: 4.4 Lead standard solution, 1g/l. Standard solutions are commercially available at this concentration. These

30、solutions may be prepared by weighing and dissolving the salt or metal of known purity. 4.5 Calibration solutions Before each series of measurements, prepare from the standard lead solution (4.4) at least five calibration solutions covering the range of concentrations to be determined.100ml of each

31、calibration solution shall contain7,5ml of nitric acid (4.1) and20ml of the matrix modifier solution(4.3) if the latter is not distributed by the automatic injection device. 5 Apparatus All the glassware used shall be previously washed by means of suitable products (such as nitric acid) and rinsed w

32、ith distilled water to eliminate any trace of lead. Use ordinary laboratory apparatus and, in particular, the following. 5.1 Digestion apparatus (seeFigure 1), made of borosilicate glass and consisting of three elements terminating with conical ground joints (5.1.1 to5.1.3). 5.1.1 Soxhlet extraction

33、 tube, of capacity200ml, equipped with a stopcock and a lateral tube connected directly to the flask (5.1.3). 5.1.2 Cooling apparatus, 35cm long, connected to the top of the Soxhlet extraction tube (5.1.1). 5.1.3 Round-bottom flask, of capacity250ml, connected to the lower part of the Soxhlet extrac

34、tion tube (5.1.1). When the stopcock is open, the device is under reflux; when, it is closed, the Soxhlet extraction tube(5.1.1) retains the condensed water and acid vapours. 5.2 Atomic absorption spectrometer, consisting of five elements (5.2.1 to 5.2.5). 5.2.1 High-resolution monochromator, allowi

35、ng a0,2nm bandwidth slit. 5.2.2 Correcting device for non-specific absorption. 5.2.3 Measuring and photoelectric reception device, with a response time not exceeding about10ms. 5.2.4 Detector and signal processing system, allowing recording of the maximum and/or integrated absorbance signal. 5.2.5 L

36、ead discharge lamp or lead hollow cathode lamp Ammonium dihydrogen phosphate (NH 4 )H 2 PO 4 10g Distilled water to make up to 1 000mlENISO 11212-3:1997 2 BSI 01-1999 5.3 Electrothermic atomizer The most widely used atomizer, for which the general conditions of use are suggested, is a graphite tubul

37、ar furnace placed in the optical axis of the spectrometer, heated by the Joule effect. The furnace shall be maintained in an inert atmosphere to avoid its destruction by oxidation when heated at a high temperature, and shall be equipped with an automatic injection device which is necessary to obtain

38、 good repeatability and to reduce the risk of contamination. 5.4 Pyrocoated graphite tube, with Lvov platform. 5.5 Pipettes and micropipettes, of suitable capacity. 5.6 Analytical balance 6 Procedure 6.1 General To avoid too high a result, it is important to decontaminate the glassware with nitric a

39、cid, to rinse it correctly, to prevent any external contamination induced by handling and by the laboratory atmosphere, and to check the purity of the reagents by means of the blank tests described in 6.4. 6.2 Preparation of test sample Thoroughly homogenize the sample. 6.3 Digestion Use the digesti

40、on apparatus described in 5.1. Weigh, to the nearest1mg, about5g of the test sample into the flask (5.1.3). Add27,5ml of nitric acid (4.1) and1ml of hydrogen peroxide (4.2). Distil under reflux for4h leaving the stopcock open. Turn the stopcock off, continue heating and distil until about20ml 1ml of

41、 liquid are recovered in the extraction tube (5.1.1). Stop heating and allow the flask to cool. Separate the flask from the extraction tube. Add 20ml of water to the digested residue in the flask, bring to the boil for a few minutes, stop heating and allow to cool. Transfer the solution to a100ml vo

42、lumetric flask, add20ml matrix modifier (4.3) (if it is not distributed by the automatic injection device), dilute to the mark with distilled water and stir. 6.4 Blank test Perform digestion under the same conditions as in6.3, replacing the test portion by5ml of water. 6.5 Electrothermal atomization

43、 programme The heating programme of the furnace mainly depends on the chemical properties of the substance to be analysed, on the matrix and on the method for approaching the isothermal conditions chosen. It is composed of four stages (6.5.1 to 6.5.4) which shall be optimized by each laboratory. 6.5

44、.1 Drying It is advisable to increase the temperature slowly up to a final temperature slightly higher than the boiling temperature of the solvent and to maintain this for at least5s. 6.5.2 Thermal pretreatment The temperature for this stage, during which the organic matrix is eliminated and the min

45、eral matrix is modified, shall be adapted by adding a matrix modifier (ammonium dihydrogen phosphate) (4.3) capable of stabilizing the substance by heat. Figure 1 Digestion apparatusEN ISO 11212-3:1997 BSI 01-1999 3 6.5.3 Atomization This stage is generally performed with a quick increase in tempera

46、ture together with no or a reduced flow of gas to ensure a maximum concentration of atoms in the optical path length. 6.5.4 Cleaning of the furnace Memory effects are possible, therefore the furnace(5.3) shall be cleaned after each injection. Cleaning is generally performed for a few seconds at maxi

47、mum temperature and gas flow rate. 6.6 Determination of the calibration curve Inject to the programmed furnace (5.3), 10l of the diluted calibration solution (4.5) and2 l of the matrix modifier (4.3) if the latter is not delivered by the automatic injection device. Measure the absorbance of each cal

48、ibration solution at a wavelength of283,3nm using the spectrometer(5.2). Draw the calibration curve by plotting the lead concentrations of the calibration solutions, expressed in micrograms per litre, as the abscissa against the corresponding values of the signal, read either in maximum absorbance o

49、r in integrated absorbance, as the ordinate. The calibration curve shall be periodically checked depending on the length of the series of analyses. 6.7 Determination Measure the absorbance of the test samples under the same conditions as the calibration solutions and compare the results with the previously plotted calibration curve. 7 Expression of results With reference to the calibration curve, determine the concentrations corresponding to the signals of the test portion and the blank. The lead concentration of the samp